Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w = map(int,input().split())
g = [['#'] * (w+2) for i in range(h+2)]
c = 0
for i in range(h):
  g[i+1][1:-1] = list(input())
  c += g[i+1][1:-1].count('#')
d = {}
d[0] = [(1,1)]
vi = set()
vi.add((1,1))
i = 0
while d[i]:
  l = d[i]
  d[i+1] = []
  for cur in l:
    for a,b in [[1,0],[0,1],[-1,0],[0,-1]]:
      to = (cur[0]+a,cur[1]+b)
      if to == (h,w):
        print(h*w-c-i-2)
        exit()
      if g[to[0]][to[1]] == '.' and to not in vi:
        vi.add(to)
        d[i+1].append(to)
  i += 1
print(-1)